Scleral Cross-linking Using Riboflavin and Ultraviolet-A Radiation for Prevention of Axial Myopia in a Rabbit Model
April 3rd, 2016
We demonstrate the effect of scleral crosslinking with riboflavin and UVA on an axial elongation rabbit eye. Axial elongation was induced in 13 day-old New Zealand rabbits (male and female) by suturing their right eye eyelids (tarsorrhaphy).
The overall goal of this procedure is to observe the effects of scleral cross-linking using riboflavin and ultraviolet-A radiation to induce axial myopia in a rabbit model. This method can help answer key questions in the scleral cross-linking field, such as, how can UVA radiation be directed to specific scleral areas. The main advantage of this technique is that it uses UVA radiation, fiber optics, and surgery to reach sceral areas of interest.
Assisting the surgical procedure will be Orly Gal-Or, a resident in Rabin Medical Center Ophthalmology Department. Before beginning the procedure, confirm a lack of response to pain reflex and use a sterile cotton swab to apply a small amount of ophthalmic ointment to the non-operated eye. Then, apply topical anesthesia to each eye.
And placing the probe perpendicular to the central cornea, use an Ultrasound A scanner to perform three axial length measurements of the eyes. Next, under an ophthalmic operating microscope, use surgical ophthalmic forceps and scissors to make a 360-degree conjunctival peritomy. Use a muscle hook to locate the four extraocular rectus muscles.
Then, isolate the muscles with two zero braided silk non-needle sutures to create four quadrants. Using a skin marker, designate one irradiation zone at the equatorial sclera, and one irradiation zone at the posterior sclera in each quadrant. Then, load a three-to five-milliliter syringe with 0.1 percent dextran-free riboflavin 5 phosphate photo-sensitizer solution and attach a 26 gauge lacrimal cannula.
Now, turn on an irradiation device with a 370 nanometer UVA light source connected to a beveled down custom made fiber optic, and set the device to 57 milliwatts per square centimeter. Twenty seconds before beginning the irradiation, move the eyeball by pulling the silk sutures in the opposite direction of the quadrant to be treated, and apply photo-sensitizer solution onto the irradiation zone. Then, use the custom made fiber optic to irradiate the selected zone for 200 seconds, applying photo-sensitizer solution to the zone every 20 seconds.
After all four quadrants have been irradiated, trim the lid margins with scissors. Then, use four zero ivory colored braided silk to gently suture the upper and lower eyelids. Apply a small amount of ophthalmic ointment onto the lid margin, and place the rabbit under a heat lamp.
When the animal is fully recovered, place it into a clean cage with new bedding. Fifty-five days after the cross-linking, use surgical ophthalmic scissors to remove the tarsorrhaphy. Then, perform three axial length measurements on each eye as just demonstrated.
In animals that underwent scleral cross-linking and tarsorrhaphy, the mean axial length decreased after eyelid suture, compared to the unoperated eye. In animals that underwent only peritomy and tarsorrhaphy, however, the mean axial length increased in the experimental eye. Indeed, eyes that underwent scleral cross-linking exhibited a lower axial length increase overall, compared to eyes that were peritomized only.
While the between-group difference in the mean axial length of the eyes that did not undergo surgery was not statistically significant. While attempting this procedure, it's important to remember to prepare all the necessary equipment in advance. After its development, this technique paved the way for researchers in the field of myopia, who explored the effects of riboflavin and UVA radiation on the retina, choroid, and sclera.
After watching this video, you should have a good understanding of how to visualize specific scleral areas of interest, and to apply focused UVA radiation treatments. Don't forget that performing surgeries on such small eyes with delicate rectus muscles can be extremely challenging and that the learning curve for perfecting the technique should be accepted. The implications of this technique extend towards the prevention of pathological myopic complications.
Though this method can provide insight into the prevention of axial myopia, it can also be applied to other conditions such as thin scleral areas.
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Overview
This study investigates the effects of scleral cross-linking using riboflavin and UVA radiation to induce axial myopia in a rabbit model. The procedure aims to enhance understanding of scleral cross-linking techniques and their application in ocular research.
Key Study Components
Area of Science
- Ophthalmology
- Experimental Surgery
- Myopia Research
Background
- Axial myopia is a significant vision problem.
- Scleral cross-linking is a potential treatment method.
- Riboflavin and UVA radiation are used in this technique.
- Understanding the effects on scleral areas is crucial for advancing treatment.
Purpose of Study
- To observe the effects of scleral cross-linking on axial elongation.
- To explore the application of UVA radiation in targeted scleral areas.
- To contribute to the knowledge base in the field of myopia treatment.
Methods Used
- Induction of axial elongation in 13-day-old New Zealand rabbits.
- Application of tarsorrhaphy to the right eye.
- Use of riboflavin and UVA radiation during the procedure.
- Monitoring of pain reflex and application of anesthesia.
Main Results
- Demonstrated effects of scleral cross-linking on eye elongation.
- Provided insights into the application of UVA radiation.
- Highlighted the surgical technique's advantages.
- Contributed to understanding myopia treatment options.
Conclusions
- Scleral cross-linking shows promise in myopia management.
- Further research is needed to optimize techniques.
- Findings may influence future ocular treatment strategies.
Frequently Asked Questions
Executive Industry Relevance
Scleral cross-linking using riboflavin and UVA radiation represents a mechanistic approach to modulate extracellular matrix remodeling in ocular tissues, offering a preclinical model for evaluating anti-myopia interventions. This technique enables target validation of scleral biomechanics in axial elongation pathways, supporting de-risking of therapeutic strategies before costly clinical translation. By demonstrating inhibition of occlusion-induced axial growth in a rabbit model, the method provides predictive confidence for pathway-specific target engagement in myopia prophylaxis.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Interrogates the causal role of scleral stiffness in axial myopia progression through direct biomechanical modulation.
- Operational Value: Enables standardized induction and suppression of axial elongation for reproducible target engagement assays.
- Predictive Value: Supports go/no-go decisions on scleral-targeted compounds by quantifying effects on eyeball elongation.
Screening & Assay Development
- Scientific Value: Establishes a quantifiable phenotypic readout (axial length via A-scan ultrasound) for compound screening in myopia models.
- Operational Value: Provides a standardized surgical and irradiation protocol to ensure assay reproducibility across laboratories.
- Scalability: Facilitates preparation of validated scleral systems for high-throughput evaluation of crosslinking agents.
Translational & Preclinical Research
- Scientific Value: Demonstrates disease relevance by preventing pathological axial elongation in a clinically relevant myopia model.
- Operational Value: Enables longitudinal monitoring of structural outcomes to support preclinical efficacy and safety profiling.
- Translational Continuity: Bridges target validation to preclinical studies by confirming mechanistic effect on scleral remodeling.
Pipeline & Workflow Integration
The method fits within the discovery continuum from target hypothesis testing to lead optimization, providing a disease-relevant system for evaluating scleral-modulating agents prior to IND-enabling studies.
- Discovery Biology: Tests hypotheses on scleral biomechanics as a driver of axial elongation, enabling mechanistic de-risking of targets.
- Screening: Delivers quantitative axial length measurements to rank compound effects on myopia progression.
- Analytics: Generates longitudinal dimensional data to support statistical comparison of treatment vs. control groups.
- Translational Research: Connects target engagement to structural outcomes, supporting biomarker-aligned advancement decisions.
- Enterprise Reuse: Establishes a reusable preclinical platform for iterative testing of crosslinking formulations and dosing regimens.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in scleral-mediated myopia by isolating the effect of crosslinking on axial growth.
- Operational Value: Standardizes a complex microsurgical and irradiation procedure for consistent cross-team execution.
- Strategic Value: Improves capital efficiency by filtering ineffective scleral targets early in discovery.
- Portfolio Impact: Enables risk-adjusted prioritization of myopia therapeutics based on validated target modulation.
Implementation Considerations
- Requires expertise in microsurgery, ophthalmic instrumentation, and UVA safety protocols.
- Depends on specialized equipment including fiber-optic UVA delivery systems and ultrasound biometry.
- Necessitates standardization of irradiation dosing, riboflavin concentration, and suturing techniques across sites.
- Involves adaptation considerations for different species, ages, and scleral thickness in model selection.
- Limited by the technical challenge of performing procedures on neonatal rabbit eyes with delicate musculature.
